SEPTA's new "smart card" fare system could mean that rail passengers would get a free ride into Philadelphia and pay a double fare on the way home.

Gated entrances with subway-style turnstiles would be installed in rail stations in the Center City zone, where riders would tap electronic-chip fare cards to board outbound trains, under a SEPTA proposal. On leaving the trains, riders would tap their cards on other electronic readers, so the appropriate fare could be deducted.

However, riders going beyond Zone 2 would need to have their fares deducted by a conductor with a handheld reader.

That scenario is outlined in bid documents prepared for three companies interested in creating SEPTA's new electronic fare system.

SEPTA officials said that the scenario is only one possible design for the fare system and that it was "premature" to discuss the proposal.

But passenger advocates and SEPTA's own citizen advisory panel were quick to criticize both the proposal and SEPTA's secretiveness about its plans.

"It's an open invitation to legal fare evasion," said Matthew Mitchell, of the Delaware Valley Association of Rail Passengers. He said passengers might ride the train into Center City for free and then take a cheaper bus or subway home.

SEPTA is "following the wrong way, both technically and in terms of communications with their customers," Mitchell said. "The planners of this have had tunnel vision - in their effort to solve one problem, which is that not all tickets are getting punched on the trains now, they have introduced a raft of new problems."

Bob Clearfield, vice chairman of SEPTA's Citizen Advisory Committee, said it was regrettable that the panel "was kept out of the design/selection process since we are the ultimate users of any package placed into service."

"By law, the agency is supposed to consult with the CAC on projects like [the new fare system], yet it has not done so," Clearfield said in a statement. "Briefings have been minimal, and requests for detailed information have been denied. This is a once-in-a-generation opportunity, and it needs to be done right."

The one-way fare scenario is outlined in a 777-page addendum to SEPTA's "New Payment Technologies System Technical Specification" dated June 29, obtained by The Inquirer through an open-records request. The scenario was first reported by the PlanPhilly.com website.

Under the proposal, SEPTA would reduce the number of rail zones from the current seven to five: Center City, Zone 1, Zone 2, Zone 3, and New Jersey. The boundaries of the new zones were not specified.

Riders coming into Philadelphia would pay no fare. Outbound riders would pay a round-trip fare. Passengers would automatically be charged for a Zone 2 fare when they got off the train, unless they tapped their "smart card" in a Zone 1 station for a lower fare. Passengers traveling beyond Zone 2 would be required to have their cards validated by a conductor with a handheld reader.

"How is that simplification?" asked Mitchell.

SEPTA general manager Joseph Casey said the prospective bidders on the new fare system were being asked to consider other scenarios as well, including one in which all stations are outfitted with fare readers and ticket vending machines.

"I share some of Matt Mitchell's concerns," said Casey. He said public review of the proposals would be invited at the "appropriate" time.

Casey said public hearings will be held before the SEPTA board votes on awarding the bid for the smart-card fare system.

SEPTA hopes to open bids for its oft-delayed fare system by late this fall and to award a contract by early next year.

The system, expected to cost at least $77 million, will take several years to install on SEPTA buses, subways, trolleys, and trains.

Mitchell said his group was taking SEPTA at its word that "public consultation will take place before a final decision is made. It's crucial that they get all these issues dealt with on the railroad side."

SEPTA has struggled to make a smart-card system work on its railroad, which is more complicated than buses or subways because of the many stations and the various fares for different destinations.

The one-way-fare scenario proposes gated entrances and fare vending machines at five Center City zone stations: 30th Street, Suburban, Market East, Temple, and University City. Fare vending machines would also be located at "selected other stations," according to the scenario description.

With the new fare system, SEPTA passengers would be able to wave a card at a sensor on a turnstile or fare box and be on their way. SEPTA says it wants a system that will allow passengers to use credit cards, prepaid SEPTA cards, and even cell phones to pay for trips.

Contact staff writer Paul Nussbaum at 215-854-4587 or pnussbaum@phillynews.com.